1. Field of the Invention
The invention relates to a clutch device that is engaged so as to selectively transmit torque from one rotating member to other two rotating members and, more particularly, to a twin-clutch device that sets an engaged state by using a functional fluid, such as a magnetic fluid, of which flowability decreases with an increase in stimulus applied from an outside.
2. Description of the Related Art
A clutch device selectively couples relatively rotatable two rotating members so that torque can be transmitted between the two rotating members. A friction clutch is generally used in a drive train of a vehicle. The friction clutch is operated by force on a pedal or hydraulic pressure. In contrast, an electromagnetic clutch is known and is able to electrically control switching operation between engagement and release. An example of the electromagnetic clutch is described in Japanese Patent Application Publication No. 4-131526 (JP-A-4-131526).
The clutch described in JP-A-4-131526 uses a magnetic fluid. A plurality of armature plates are secured to a rotary shaft of the clutch, and the armature plates are accommodated in a fluidtight state inside a closed chamber formed in a pulley. The closed chamber is filled with the magnetic fluid. An electromagnetic coil is provided for the clutch and applies magnetism to the magnetic fluid for magnetization. Thus, by energizing the magnetic coil, a shearing coefficient (shearing force) of the magnetic fluid is increased to transmit torque between the rotary shaft and the pulley.
With the clutch configured as described in JP-A-4-131526, the clutch may be engaged by energizing the electromagnetic coil, and the clutch may be released by deenergizing the electromagnetic coil. Thus, it is possible to electrically perform so-called on/off control of the clutch. However, transmission and interruption of torque as in the above manner is applicable only to between a single rotary shaft and a single pulley. Therefore, as in the case of a clutch used in a so-called twin-clutch transmission, when torque is transmitted or interrupted between a single drive shaft and two intermediate shafts, two sets of mechanisms, such as the closed chamber, electromagnetic fluid and electromagnetic coil, which are described in JP-A-4-131526, need to be provided. For this reason, the size of the configuration increases as a whole. This may deteriorate mountability or increase cost.